Switch contact finger



March 18, 1930. A, COHN ET AL 1,751,444

SWITCHQCONTACT FINGER Filed Jan. 24, 1927 I FL A.

Inventors: Alfred Cohn, Adolf'KLirnrnel, y TheirAttorney Patfented Mar.18, 1930 \UNITED STATES IPATENTIOFFICE ALFRED man, or cmto'rrnnnune, ANDAnon? KUMMEL, or WILMERSDORF, ena- YORK MANY, ASSIGNOIBS T GENERALELECTRIC COMPANY, A CORPORATION OF NEW swzrcn coiyrnor rmenn Applicationfll'ed January24, 1927, Serial No. 168,033, and in Germany February 2,1926.

The invention relates to contact fingers for electric switches,particularly contact fingers constructed to permit the ready andconvenient removal and replacement of the contact 6 elements without theuse of tools.

With such contact fin ers, ordinarily there is considerable chance 0taccidental displacement or even disengagement of the contact elementsduring service due to the readily de- 10 tachable construction that isintended to permif easy removal of the contact elements at wi l. a

' The principal object of the present inven: tion is to provide animproved construction of contact finger that not only readily permitsremoval and replacement of the contact element at will without the useof tools, but also efiectively insures against accidental derangement ordisengagement of the contact element under service conditions.

In accordance with the preferred form of the present invention, thecontact element is secured to its cooperating supporting member by meansof a double headed bolt which passes through slots, preferably ofkeyhole shape, formed in the contact element as Well as the support andcarries a spring for yieldingly pressing the contact element intoengagement with the support. Removal and replacement of the contactelement is effected simply by manipulating the headed bolt so that itmay be retracted through the slots and thereby release the contactelement. The keyhole shape of the slots permits the body "of the bolt tobe slid into the restricted portions thereof and thereby insure againstaccidental dis placement of the parts. To further insure that thecontact and support are maintained in operative engagement, one of theseelements preferably is provided with a projectin lug or tongue that fitsinto the slot in the otl ier element thereby preventing accidentaldisengagement of the bolt from the restricted ortions' of the keyholeslots. Also with the ody of the bolt of rectan ular or other noncircularcross section thefiiolt as well as the interconnected contact andsupport are prevented from turning beyond a limitedv amount.

One form of contact finger constructionem bodying the present inventionis shown in and secured in place by the ready removable bolt 12- and thespring 13. As shown more clearly in Fig. 2, the support 10 is providedwith a slot 14 of keyhole shape having an enlarged portion 15 and anelongated restricted portion 16. The contact element 11 likewise isprovlded with a slot 17 of keyhole shape having an enlarged ortion 18and a restricted portion 19. A suita le contact tip 20 is fixedlysecured to one end of the contactelement l1 by the bolt 21 as shown,altho, it will be understood that the tip may be secured by anothermeans such as riveting, welding or even may be formed inte ral with thecontact element if desired. T e other end of the contact element isprovided with a projection, preferably'in the form of a bent over tongue22 as indicated, of a suitable size to fit into the enlarged portion 15of the slot in the supporting element 10.

The double headed form of the bolt 12'is' shown in Fig. 3 and the head23 is sufliciently enlarged to engage with the convolutions of thespring 13 while the head 24 may be smaller, as indicated in the drawing,to facilitate the assembling of the spring 13 and the.

bolt. Furthermore, the head 24 of the bolt is pro ortioned to readilypass through the keyliole slots 14 and 17 respectively, in the supportand the contact element, as will be more fully pointed out in connectionwith the manner of assembling and disassembling the contact element. Thebody'portion 25 of the bolt is of rectangular cross-section andproportioned to fit snugly into the restricted portion 19 of the slot17, as shown in. Fig. 2. If desired, a cable connector terminal 26 maybe provided as shown in Fig. 1 for connecting acurrent conductor to thecontact finger. However, connection may be made directly to thesupporting element if desired and the current will be conducted to thecontact element 11 through the tongue 22 and the bolt 12 as well as theother engaging portions of the contact element and the support.

In assembling the various parts of the contact finger, the spring 13 isfirst placed upon the body 25 of the bolt 12 by slipping the spring overthe head 24 or in any other suitable manner. The end 24: of the boltthen is passed through the slot 17 in the contact ele- Then the bolttogether with the-contact element 11 is slid along to bring the body ofthe bolt to the end of the restricted portion 16 of the slot 14 and thetongue 22 into the enlarged portion 15 of the slot 14. The various partsof the contact finger are now assembled in their operating relation withthe keyhole slots disposed in reversed overlapping relation, as shown inFig. 2. Due to the compression of the spring 13 during the assemblingoperation, the contact element 11 is firmly pressed against thesupporting element 10, thereby insuring that the ton ue 22 remains inengagement with the enlarged I portion 15 of the slot in the support.However, the contact element 11 is free to yield readily upon theengagement of the tip with a co-operating contact element such as thesegment of a drum controller or the like.

As the body of the bolt 12 is of rectangular section, it engages withthe sides of the restricted portion 19 of the slot 17 and therebyefi'ectively prevents any rotation of the bolt in the slot. However,limited lateral displacement of the contact element relative to thesupporting element is ermitted by the loose engagement of the si es ofthe body of the bolt with the restricted portion 16 of the slot' 14.Furthermore, the contact element 11 is free to tilt aboutits'longitudinal axis to-a limited extent so as to readily permit thecontact tip 20 to align itself with a cooperating contact.

- 11 order to obtain a greater tilting movement of the contact element11, the end thereof having the upturned tongue 22 may be tapered, asindicated in Fig. 4. In this case,

the tongue 22 acts somewhat as a swivel or ball joint more readily topermit tilting ofthe contact element 11 about its longitudinal axis.

In removing the contact element 11, the procedure is just reversed fromthat previously described in the method of assembling. The tongue 22first is lifted out of the slot against the compression of spring 13 andthe contact element 11, together with the bolt 12,

slid to the right to permit the head 24E of the supporting elementwithout the necessity of using a rivet, screw, or other fixed connectionrequiring the use of tools. At the same time, whenthe various parts ofthe contact finger are assembled in operative relation there ispractically no opportunity for derangement or disengagement of the partsof the finger during service.

Nhat we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A contact finger comprising a supporting element and a contactelement, each having'a slot therein of substantially keyhole shape andone of said elements having a projection adapted to engage the enlargedend portion of the key-hole shaped slot of the other element when therestricted ends of the key-hole shaped slots in the two elements aredisposed in. reversed overlapping relation, and a headed boltproportioned to separately pass through the slot in each element fordetachably locking the elements together with the key-hole slots thereindisposed in said reversed overlapping relation.

2. A contact finger comprising a supporting elementand a contactelement, each having a slot therein of substantially keyhole shape, anda double headed bolt proportioned to separately pass through the slot ineach element for detachably locking the elements together with therestricted portion of the keyhole slots disposed in reversed overlappingrelation, the body of said bolt being of .rectangular cross section andarranged to be slid, into non-rotatable engagement with the sides of therestricted portion of the keyhole slot in one of said elements after thehead of the bolt is passed through the slot therein,

and said contact element having a bent up end for engaging with theenlarged portion of the keyhole slot in the supporting element after thebolt is slid into the restricted portion thereof, and a compressionspring disposed on said bolt for maintaining the contact element and thebolt in yielding engagement with the supporting element.

In witness whereof, we have hereto set our hands this 5th day of January1927.

- DR. A. ooHN.

ADOLF KUMMEL.

